The transparent conductive film is a film having good electrical conductivity, and a high visible light transmittance. The transparent conductive film has been widely used in flat panel displays, photovoltaic devices, touch panels and electromagnetic shielding, and other fields, having a very broad market space.
ITO has dominated the market of the transparent conductive film. However, in most practical applications such as a touch screen, production processes including exposure, development, etching, cleaning, and so on, need to be carried out to make the transparent conductive film patterned, i.e. a fixed conductive region and an insulating region are formed on the surface of the substrate based on the patterned design. In comparison, forming a metal grid directly on a specified region of the substrate by means of the printing method can eliminate the need for a patterned process, and has such advantages as low pollution and low cost. The grid line is made of a metal having good electrical conductivity and which is impenetrable to light, with the line width below resolution of the human eye; a region without lines is a light transmitting region. The surface square resistance and light transmittance of the transparent conductive film can be controlled within a certain range by changing width and grid shape of the lines.
Japanese companies, Dai Nippon Printing, Fuji Film and Gunze, and German company, PolyIC all use the printing method and obtain the patterned transparent conductive film having excellent properties. Wherein the graph obtained by PolyIC has a resolution of 15 um, a surface square resistance of 0.4-1 Ω/sq, and a light transmittance greater than 80%.
The above metal grid film is generally designed according to graphs, with the metal grid of a regular shape laid in the conductive region; however, the insulating region is blank.
In the prior art of preparing the patterned transparent conductive film, compared with the traditional ITO film, forming the metal grid directly in the specified region of the flexible substrate material by means of a printing method or a silver salt method can eliminate the need for a patterned process, and has such advantages as low pollution and low cost. However, the existing metal grid is mostly a grid of a regular shape, and may produce obvious Moire stripe in application. Besides, the conductive region of the film has the metal grid, while the insulating region does not, and this transmittance difference may make users vaguely see the graphs in the conductive region, thus affecting the overall appearance.
Therefore, the prior art has the following defects:
The Moire stripe phenomenon: the conductive region of the film is a grid having an irregular shape, and attaching this transparent conductive film to the surface of LCD may cause obvious Moire stripe, which influences the visual effect. This is because the LCD pixel unit is a rectangular unit having an irregular shape, and between the pixels are black lines that have a regular shape and a periodic distribution. However, the periodic opaque lines of the conductive film may form a periodic shelter with the black lines of LCD, which further macroscopically appear to be the Moire stripe phenomenon. In addition, due to the same principle, the significant Moire stripe can also be produced through lamination of two pieces of the regular grid conductive film. This phenomenon undoubtedly severely restricts application of the patterned transparent conductive film based on the metal grid.
Transmittance difference: The conductive region of the film has the metal grid, whose transmittance will be attenuated following the shading ratio of the grid lines; while the insulating region does not have the grid lines, and therefore the transmittance of this region is certainly greater than that of the conductive region. When applied to the display field, this transmittance difference may make users vaguely see the graphs in the conductive region, thus affecting the overall appearance.